1. Technical Field
The present invention relates to a connection structure having, for example, an electro-conductive film provided on an insulation layer and another electro-conductive film provided under the insulation layer, where the first-mentioned electro-conductive film and the second-mentioned electro-conductive film are electrically connected to each other. The present invention further relates to an electro-optical device that adopts such a connection structure for electric connection between electro-conductive films such as pixel electrodes, wiring, though not limited thereto. In addition, the present invention relates to a method for manufacturing an electro-optical device having such a connection structure.
2. Related Art
In the configuration of a liquid crystal device, which is a non-limiting example of an electro-optical device having a related-art connection structure, each of pixel electrodes that are made of transparent electro-conductive films such as indium tin oxide (ITO) or the like is electrically connected to a relay layer, which is provided below the pixel electrode, via a contact hole. One technical problem of the related-art connection structure, which has a pixel electrode and a relay layer that are electrically connected to each other via a contact hole, lies in that it is difficult to provide a wide open area (i.e., a region that passes light) in a pixel layout configuration. Specifically, in order to establish an electric connection between a relay layer, which is not transparent, and a transparent pixel electrode via a contact hole, it is necessary to overlap a part of the relay layer and the pixel electrode in a plan view, or in other words, underlay a part of the relay layer with respect to the pixel electrode. For this reason, the opaque relay layer substantially narrows, within the entire region of a pixel, the dimension of the open area, which is an active area through which light can be transmitted/reflected. When forming a contact hole at an area where opaque constituent elements that block light, including but not limited to, wiring, a light-shielding film(s), and a semiconductor device(s), are provided, it is necessary to allocate a space margin in consideration of positional alignment between two types of masks used for removing a region of an insulation layer at which the contact hole is supposed to be bored. Since it is necessary to allocate a margin space, the ratio of non-open area to the entire region of a pixel is lowered. This means that it is difficult to enhance display performance by increasing an aperture ratio of the pixel (i.e., the percentage of the light-transmissive/reflective open area that occupies the region of the pixel).
As a known technical solution to the above-identified problem, JP-A-11-3938 discloses a connection structure in which two electro-conductive patterns are electrically connected to each other via a small contact region, where one of the above-mentioned two electro-conductive patterns is formed in a layer that is not the same as that of the other electro-conductive pattern with an insulation film (i.e., insulation layer) being interposed or sandwiched therebetween.
Disadvantageously, in the configuration disclosed in JP-A-11-3938, it is difficult to make the size of a connection electro-conductive film compact because the connection electro-conductive film extends onto the surface of an under-layer electro-conductive pattern of the above-mentioned two electro-conductive patterns. For this reason, the configuration disclosed in JP-A-11-3938 has a technical disadvantage in that the open area of a pixel is narrowed by such an overlapping portion of the connection electro-conductive film that extends onto the surface of the under-layer electro-conductive pattern of the above-mentioned two electro-conductive patterns.
On the other hand, when the source region of a pixel switching TFT, which is provided in each pixel region for the purpose of supplying an image signal to the corresponding one of pixel electrodes, and the drain region thereof are electrically connected to a data-line side wiring region and a pixel-electrode-side wiring region via contact holes (i.e., each via a contact hole), respectively, a coupling capacitance is undesirably generated between the data-line side wiring region and the pixel-electrode-side wiring region because of a potential difference therebetween. Then, the coupling capacitance generated between the data-line side wiring region and the pixel-electrode-side wiring region could cause the problem of defective display such as a horizontal crosstalk or other similar problems at the time of operation of an electro-optical device.